In conventional refrigeration or cooling systems, an expansion valve is installed and functions to expand and meter the flow of refrigerant into the evaporator heat exchangers and cold plates, and to maintain appropriate superheat conditions at the compressor's first-stage inlet. Heretofore, expansion valves most prominently have been installed in piping leading to the evaporator, usually separate from the evaporator assembly. This results in the evaporator and the expansion valve occupying a considerably large space. Such an expansion valve also is subject to vibrations and jolts, particularly when used in vehicular applications. Torque produced by the weight of the expansion valve acts on connections between the piping and the valve and between the piping and the evaporator, thereby causing breakage of the joints and leaking of the refrigerant. The evaporator's own weight itself acts on the connections between the piping and the expansion valve and also may cause breakage and resulting leakage.
Evaporator and expansion valve arrangements or systems as described above are used primarily in commercial applications and, often, in automotive applications, but such systems are not readily applicable for use in densely packaged envelopes typical of aircraft vapor cycle systems. Problems in terms of weight, space, plumbing or piping complexity, and reliability are encountered when such evaporator and valve systems are utilized in aircraft applications.
A typical commercial evaporator and expansion valve system is shown in U.S. Pat. No. 3,570,263 to Tobias, dated Mar. 16, 1971. A system such as the Tobias system includes a remote temperature sensing bulb and an equalizer line in addition to the other plumbing or piping connections described above. Such a system obviously would create packaging or envelope problems in densely packed envelopes typical of aircraft vapor cycle systems. In addition, the small capillary tube which connects the remote sensing bulb to the evaporator head is prone to breakage, particularly in high vibration environments.
Attempts have been made to solve the above problems as shown in the disclosures of U.S. Pat. Nos. 4,114,397 to Takahashi et al, dated Sept. 19, 1978, and 4,149,390 to Iijima et al, dated Apr. 17, 1979. In both of these patents, the thermal expansion valve is incorporated in an assembly of plates located at one end of a tube/fin evaporator construction. Although the systems shown in these patents eliminate much of the piping and the connections of commercial installations, they simply incorporate the valve as a mounting at one end of the evaporator and do not take advantage of the evaporator itself for comprising integral components of the thermal expansion valve assembly.
This invention is directed to solving many if not all of the above problems by incorporating a thermal expansion valve as an integral assembly with the evaporator itself, whereby portions of the evaporator comprise portions of the thermal expansion valve in an integrated system or assembly.